Microwave Chocolate Fudge

3 cups semisweet chocolate chips
1 (14 ounce) can sweetened condensed milk
1/4 cup butter or margarine, diced
1 cup chopped walnuts

Combine first 3 ingredients in a 2-quart glass bowl. Microwave at MEDIUM (50% power) 4 to 5 minutes, stirring at 1 1/2 minute intervals.

Stir in chopped walnuts, and pour mixture into a buttered 8-inch square dish. Chill at least 2 hours.

Cut into squares.